To keep the cost of making integrated circuits low, manufacturers have sought processing equipment such as vacuum systems capable of handling high product volume in minimal time i.e. high thruput. The ability, however, to realize minimal process time and high process volume is problematical.
The making of integrated circuits used in electronic equipment today requires elaborate and complicated manufacturing procedures. These procedures make high thruput difficult to realize. The electronic devices included in integrated circuits are typically made by controllably introducing impurities into a silicon substrate. The impurities are positioned in the substrate to defining regions of varying conductivity type necessitated for device operation. Following formation of the impurity regions, the devices are provided with electrical leads and interconnected to form circuits by depositing one or more metallization layers at the substrate surface.
To assure purity and adherence of the metallization and to prevent contamination of the substrate surface, manufacturers are compelled to apply the interconnect metallization while the substrates are under vacuum, i.e. in a vacuum system. In the system chamber, vacuum etching and cleaning steps are performed to expose and prepare the substrate surface for receiving the metal to be deposited. Often such steps require r.f. and d.c. electrical energy as, for example, where reactive ion etching or sputter etching processes are used. Since the sources of electrical energy are typically located externally of the vacuum chamber for simplicity and economy of chamber space, it is necessary to feed the electrical energy into the chamber while maintaining the chamber vacuum. The supply of r.f. energy in these cases can be difficult especially where high thruput is sought.
Additionally, manufacturers have found it necessary to supply mechanical energy to the vacuum system chamber. To assure uniformity of processing, it has been found desirable to move the substrates through the chamber during processing. Typically, this is done by rotating the holder which carries the substrates. By rotating the substrate holder, process nonuniformity in time and space is distributed over the substrates to render them more uniform. As in the case of electrical energy supply, because the source of rotational energy is for simplicity and economy of chamber space located externally of the chamber, it becomes necessary to feed the rotational energy into the chamber while maintaining the chamber vacuum. Like the supply of electrical energy, the supply of mechanical energy can be difficult especially where high thruput is sought.
Because of these energy supply requirements, it is difficult to obtain high thruput. To get high thruput, manufacturers use larger volume vacuum chambers into which they load high capacity holders for carrying larger number of substrates. Uses of high capacity holders, however, in combination with conventional fixed mount electrical and mechanical feedthrough increases process time. As the holder capacity gets larger it becomes more time consuming to load it to a conventional feedthrough. In the case of large capacity holders, the holder with substrates can weigh upwards of 40 pounds and extend to over 30" in diameter. Because stationary feedthroughs are typically located centrally of and proximate to the vacuum chamber dome to enable proper positioning of the substrates during processing, it becomes difficult for operators to quickly position and attach the substrate holders to the feedthrough. The additional time required diminishes thruput.
While apparatus for more conveniently mounting substrate holders and supplying required electrical and mechanical energy have been proposed, as for example commercially available trolley type mount feedthroughs, their designs have not been intended to include r.f. and d.c. electrical capability as well as the rotational mechanical capability. Additionally, these feedthroughs typically suffer from inconsistent and non-uniform supply of rotational motion and electrical energy.